System and method of detecting a failed friction element

Abstract

A system includes a friction element having a driving mechanism and a driven mechanism. At least one of the driving mechanism and the driven mechanism is configured to rotate. A drive unit is configured to provide a torque to at least one of the driving mechanism and the driven mechanism. A control processor is configured to diagnose a friction element failure based on a slip speed, which is the difference between rotational speeds of the driving mechanism and the driven mechanism. The control processor is further configured to induce a slip condition as part of a shift process and diagnose the friction element failure if the derived slip speed is substantially zero after inducing the slip condition.

1. A system comprising:
 a friction element having a driving mechanism and a driven mechanism, wherein the driving mechanism and the driven mechanism are selectively engageable with and disengageable from each other during a shift process, and wherein at least one of the driving mechanism and the driven mechanism is configured to rotate; 
 a drive unit configured to provide a torque to at least one of the driving mechanism and the driven mechanism; and 
 a control processor configured to diagnose a failure of the friction element based on a derived slip speed defined by the difference between rotational speeds of the driving mechanism and the driven mechanism, wherein the control processor is further configured to:
 induce a slip condition as part of the shift process by transmitting a torque signal to the drive unit commanding different rotational speeds from the driving and driven mechanisms; and 
 diagnose the friction element failure if the derived slip speed is substantially zero after inducing the slip condition. 
 
 
     
     
       2. A system as set forth in  claim 1 , wherein the control processor is configured to derive the slip speed and determine that the driving mechanism is engaged with the driven mechanism if the derived slip speed is substantially zero. 
     
     
       3. A system as set forth in  claim 1 , wherein the control processor is configured to transmit at least one torque signal to the drive unit to cause the driving mechanism to rotate at a different speed than the driven mechanism to induce the slip condition. 
     
     
       4. A system as set forth in  claim 1 , further comprising a first sensor configured to measure the rotational speed of the driving mechanism and a second sensor configured to measure the rotational speed of the driven mechanism. 
     
     
       5. A system as set forth in  claim 1 , wherein the drive unit includes a first torque actuator configured to provide a torque to the driving mechanism and a second torque actuator configured to provide a torque to the driven mechanism. 
     
     
       6. A system as set forth in  claim 1 , wherein the control processor is configured to determine an intended position of the driving mechanism relative to the driven mechanism and generate a command signal representative of the intended position. 
     
     
       7. A system as set forth in  claim 6 , further comprising a hydraulic system operatively connected to the friction element and in communication with the control processor, wherein the hydraulic system is configured to receive the command signal and cause the driving mechanism to at least one of engage and disengage the driven mechanism based on the command signal. 
     
     
       8. The system of  claim 1 , wherein the friction element is one of a clutch and a brake in a vehicle transmission. 
     
     
       9. A system comprising:
 a friction element having a driving mechanism and a driven mechanism, wherein at least one of the driving mechanism and the driven mechanism is configured to rotate, and wherein the driving mechanism and the driven mechanism are selectively engageable with and disengageable from each other; 
 a drive unit configured to provide a torque to at least one of the driving mechanism and the driven mechanism; 
 at least one sensor configured to directly or indirectly measure the rotational speed of at least one of the driving mechanism and the driven mechanism; and 
 a control processor configured to:
 induce a slip condition as part of a shift process by transmitting a torque signal to the drive unit commanding different rotational speeds from the driving and driven mechanisms; 
 determine an expected slip speed between the driving and driven mechanisms in response to the induced slip condition; 
 derive a slip speed from the rotational speeds measured by the at least one sensor; 
 compare the derived slip speed to the expected slip speed; and 
 diagnose a failure of the friction element based on a difference between the derived slip speed and the expected slip speed. 
 
 
     
     
       10. A system as set forth in  claim 9 , wherein the control processor is configured to diagnose the friction element failure if the measured slip speed is substantially different than the expected slip speed. 
     
     
       11. A system as set forth in  claim 9 , wherein the control processor is configured to determine that the friction element is working properly if the derived slip speed is substantially the same as the expected slip speed. 
     
     
       12. A system as set forth in  claim 9 , wherein the drive unit includes a first torque actuator configured to provide a torque to the driving mechanism and a second torque actuator configured to provide a torque to the driven mechanism. 
     
     
       13. A system as set forth in  claim 9 , wherein the control processor is configured to determine an intended position of the driving mechanism relative to the driven mechanism and generate a command signal representative of the intended position. 
     
     
       14. A system as set forth in  claim 13 , further comprising a hydraulic system operatively connected to the friction element and in communication with the control processor, wherein the hydraulic system is configured to receive the command signal and cause the driving mechanism to at least one of engage and disengage the driven mechanism based on the command signal. 
     
     
       15. A diagnostic system comprising:
 at least one speed sensor configured to measure a rotational speed of at least one of a driving mechanism and a driven mechanism of a friction element, wherein the driving mechanism and the driven mechanism are selectively engageable with and disengageable from each other; and 
 a control processor in communication with the at least one speed sensor, and configured to diagnose a failure of the friction element based on a derived slip speed defined by a difference between the rotational speed of the driving mechanism and the rotational speed of the driven mechanism; 
 wherein the control processor is further configured to:
 transmit a torque signal commanding different rotational speeds from the driving and driven mechanisms to thereby induce a slip condition as part of a shift process; and 
 diagnose the friction element failure if the derived slip speed is substantially zero after inducing the slip condition. 
 
 
     
     
       16. A diagnostic system as set forth in  claim 15 , wherein the control processor is configured to determine that the driving mechanism is engaged with the driven mechanism if the derived slip speed is substantially zero. 
     
     
       17. A diagnostic system as set forth in  claim 15 , wherein the control processor is configured to diagnose that the friction element is working properly if the derived slip speed is a substantially non-zero value after inducing the slip condition. 
     
     
       18. A diagnostic system as set forth in  claim 15 , wherein the control processor is configured to diagnose the friction element failure if the derived slip speed is substantially zero after inducing the slip condition. 
     
     
       19. A diagnostic system as set forth in  claim 15 , wherein the control processor is configured to transmit at least one torque signal to a drive unit to cause one portion of a friction element to rotate at a different speed than another portion of the friction element to induce the slip condition. 
     
     
       20. The diagnostic system as set forth in  claim 15 , wherein the friction element is a clutch, and wherein:
 the at least one speed sensor includes a first and second speed sensor each configured to measure a rotational speed of the driving and driven mechanism, respectively; 
 the rotational speeds of the driving and driven mechanisms are provided via a first and a second motor, respectively; and 
 the control processor induces the slip condition as part of a shift process in which torque is transmitted from the driving mechanism to the driven mechanism to thereby cause the driven mechanism and the driving mechanism to rotate at different speeds.